The invention relates to modified polymers and polymer blends useful for waste disposal or for agricultural purposes to provide water or UV degradable materials which are environmentally safe. The materials are designed to degrade upon exposure to water or to UV light to environmentally safe naturally occurring materials. The modified polymers and polymer blends when used are also usable for garbage bags or other waste disposal purposes can be incinerated since upon burning only environmentally safe materials are produced.
It is now recognized that many plastic materials useful for packaging as well as waste disposal present serious environmental problems because they either do not degrade in landfills or produce toxic components upon incineration. More and more attention has been devoted to environmentally safe plastic materials, particularly since Congressional hearings have determined that over 135 thousand metric tons per year of plastic is discarded at sea alone with some 639,000 plastic containers and bags tossed into the ocean every day. In addition to this intolerable situation, the amount of plastic materials used for packaging as well as garbage disposal which do not degrade has caused landfill areas previously thought to be entirely adequate for urban disposal sites to become filled and unusable. Waste disposal has become a very serious problem in this country as well as world-wide.
Accordingly, there is a need to provide plastic materials suitable for packaging and waste disposal which at the same time will also be biodegradable to products which are environmentally safe.
Recently, it has been determined that high carbohydrate waste presently produced in the United States as cheese whey and in conjunction with potato processing facilities is convertible in an environmentally benign process to provide a feed stream for lactic acid. Lactic acid is desirable because it is a naturally occurring compound which degrades to environmentally safe products. In addition, it has been discovered that oligomers of polylactic acid are not only environmentally safe but preferable and are useful as plant growth promoters, see U.S. Pat. No. 4,813,997 to Kinnersley et al., issued Mar. 21, 1989. With the discovery by Kinnersley et al. and the conversion of high carbohydrate food waste to feed stocks for lactic acid, a result of research at Argonne National Laboratory, it has become feasible through the present invention to formulate various copolymers and blends of polylactic acid for a wide range of agricultural and packaging uses which meet all the objectives set forth above and provide environmentally safe materials to replace presently used plastics that are difficult to dispose of in a safe manner.
Accordingly, it is an object of the invention to provide water and/or UV light degradable modified polylactic acid polymers or blends thereof useful for the agricultural and/or packaging and/or waste disposal industries.
Another object of the invention is to provide water degradable or UV light degradable polylactic acid polymers and copolymers which may be used as agricultural coatings and mulches which degrade in the field to provide environmentally safe materials as well as plant growth promoters.
Another object of the invention is to provide a water degradable modified polylactic acid polymer comprising a copolymer of monomers of lactic acid and a modifying monomers selected from the class consisting of ethylene glycol, propylene glycol, p-dioxanone, 1,5 dioxepan-2-one, 1,4 -oxathialan-2-one, 4,4-dioxide and mixtures thereof, wherein the ethylene glycol is present in the range of from about 5% by weight to about 40% by weight, wherein the propylene glycol is present in the range of from about 5% by weight to about 40% by weight, wherein the p-dioxanone, 1,5 dioxepan-2-one or the 1,4-oxathialan-2-one, 4,4-dioxide is present in the range of from about 2% by weight to about 40% by weight, the modifying polymer not exceeding about 40% by weight of the modified polylactic acid copolymer.
A still further object of the invention is to provide a water and UV degradable polylactic acid polymer comprising a copolymer of polylactic acid and a modifying monomer selected from the class consisting of p-dioxanone present in an amount up to about 20% by weight, 1,5 dioxepan-2-one present in an amount up to about 20% by weight, and 1,4 oxathialan-2-one, 4,4 dioxide present in an amount up to about 20% by weight, or mixtures thereof, the modifying monomer being present in an amount not greater than about 20% by weight.
Still another object of the invention is to provide a water degradable polylactic acid polymer comprising an alloy of polylactic acid and high molecular weight polyethylene oxide wherein the high molecular weight polyethylene oxide is present in the range of from about 2 to about 50% by weight.
A final object of the invention is to provide a method of applying an active material selected from the class of seeds, seedlings, pesticides, herbicides, fertilizers and mixtures thereof of an to agricultural site comprising providing a copolymer of monomers of lactic acid and a modifying monomer selected from the class consisting of ethylene glycol, polypropylene glycol, p-dioxanone, 1,5 dioxepan-2-one, 1,4-oxathialan-2-one, 4,4-dioxide and mixtures thereof, wherein the ethylene glycol is present in the range of from about 5% by weight to about 40% by weight, wherein the propylene glycol is present in the range of from about 5% by weight to about 40% by weight, wherein the p-dioxanone, 1,5 dioxepan-2-one or the 1,4-oxathialan-2-one, 4, 4-dioxide is present in the range of from about 2% by weight to about 40% by weight, the modifying polymer not exceeding about 40% by weight of the modified polylactic acid polymer, forming a combination of the copolymer and the active ingredients wherein the active ingredients are present in the range of from about 60% to about 98% by weight of the combination, and applying the combination to the agricultural site.
The invention consists of certain novel features and a combination of parts hereinafter fully described, and particularly pointed out in the appended claims, it being understood that various changes in the details may be made without departing from the spirit, or sacrificing any of the advantages of the present invention.